Rheostat



L. KEBLER,

RHEOSTAT. APPLICATION HL! ZD MAR. 14.1919.

Patented Jan. 10, 1922.

2 SHEETS-SHEET I.

L. KEBLER.

RHEOSTAT.

APPLICATION FILED MAR-14,1919. 1,402,772, Patented Jan. 10,1922.

2 SHEETS-SHEET 2.

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UNITED STATES PATENT OFFICE.

LEONARD KEBLER, or BRONXVILLE, new YORK, ASSIGNOR ro wan-n LEONARD nnncmnrc COMPANY, A CORPORATION or NEW YORK.

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To all whom it may concern: I

Be it known that I, Lnonano lineman, a citizen of the United States, residing at Bronxville, in the county of estchester and State of New York, have invented certain new and useful Improvements in Rheostats, of which the following is a specification.

One object of my invention is to provide a new and improved rheostat adaat-ed to avoid undue overheating. Another object of my invention relates to distributing the resistance elements of a rheostat in such a way as to prevent undue local overheating. Still another object of my invention relates to balancing the stresses on the pivoted adjustable contact arm of the rheostat. These and other objects will be appreciated upon consideration of a specific embodiment of my invention which is disclosed in the following specification taken with the accompanying drawings. It will be understood that modifications may be made within the scope of my invention. Referring to the drawings,

Fig. 1 is a top plan view of the rheostat which I have chosen to disclose as exemplifying the invention.

Fig. 2 is a side elevation,

Fig. 3 is an inside face view of one of the two main plates and of the contact carrying pivoted arm,

Fig. 4 is a wiring diagram, and

Fig. 5 is an enlarged detail elevation of a fragment of one of the plates with the resistanceconductors applied thereto, but before they have been covered with enamel.

The main rheostat frame comprises two cast iron plates, a rear plate 5 and a front plate 6. Each of these plates 5 and 6 is surrounded by an inwardly directed flange and each plate carries four inwardly directed projections 7 which butt against each other in pairs and serve definitely to space the two plates 5 and 6 apart. Through the projections 7 extend bolts 9 secured by'nuts '8 thus uniting the two plates 5 and 6 in one rigid frame. The bolts 9 are extended at 10 to afford means of attachment to a wall.

The inside faces of the plates 5 and 6 are covered with an insulating enamel 32, then the resistance wires, such as 37 in Fig. 5, are applied and attached to the contact studs 24. Each stud 24 has a foot 24' and another part 24 that is doubled and pinched tightly over Specification of Letters Patent. Patented Jan 10, 1922 Application filed March 1919. "serial No. 282,575.

theresistance wire 37 to make good electrical engagement therewith. After the resistance conductor, such as 37, and the contact terminals 24 are assembled as shown in Fig.

another coat of enamel 32 is applied, covering the wires 37 and the parts 24 and 24" ot the studs 24 and holding them in definite relation to the plates 5 and 6.

The plate 5 carries an inwardly projectng p votal support 13 on which is pivoted the arm 12 extending up between the plates 5 and 6 and carrying a handle 20 overhanging the front plate 6. Near its upper end the arm 12 has front and rear projections 21 carrying the rearcontact shoe 22 and the front contact shoe 23, respectively. pressed outwardly by the springs 28 and 29 and engaging the contact studs 24 on the rear and front plates 5 and 6 respectively.

The stop 61 is provided to limit the lefthand movement of the contact arm 12, which carries an insulated piece 62 to engage therewith. On the right, the arm 12 carries an insulated yoke 63 with which the projections 7 cooperate to act as a stop. The yoke 63 can readily be replaced by one that is longer or shorter as may be desired, so as to adjust the extent to which the rheostat may cut out resistance, as will be explained i later. 1

The wiring will be explained particularly with. reference to Fig. 4 lay-tracing the circuit through the rheostat and an associated storage battery 65 from supply means 64,

64. The resistance elements on the two plates are in this embodiment in multiple in the circuit by virtue of cross connectors 30, 4-2 and 34, as will be shown. Starting from the main-64, the circuit goes through the battery 65 to the rheostat terminal 40, where it divides by reason of the connector 30; the circuitfor onlyone plate is shown in Fig. 4.

From the terminal 40, the circuit goes through the residual resistance 35 to the stud 66 (Fig. 3), thence over the wire 31 to the common stud 42 to which like wires 31 are connected from both plates 5 and 6. From 42, there is a conductor 43 back of plate 5 which goes to the stud 44 at the extreme right of the rheostat. Each plate 5 and 6 has such a stud 44 and these two studs are connected by the conductor 34. From the stud on each plate, the circuit goes as shown in Fig. 4 for rear plate 5 through the conductors 36 to the contact arm 12, thence lbs ments are designated 36.

tent to which the resistance elements 36 may be cut out of circuit. Accordingly, the re sistance elements 35 may be referred to as residual and fixed, the resistance elements 36 as semi-adjustable or semi-fixed and the resistance elements 37 as fully adjustable. It will be seen that the current goes through fixed residual resistance 35 at one side of the rheostat, then through the semi-adjustable resistance 36 at the extreme opposite side, thenin order through more or less of the fully adjustable resistance 37 in the middle of the board, and that the resistance elements 37 which would be the first to be cut out are located closest in space to the residnal resistance 35.

As shown in the particular example which I have. chosen to illustrate my invention, a storage battery 65 is charged from line 6464. by the aid of my improved rheostat, and the rheostat is employed to give a suflicient voltage drop therethrough to compensate for the excess of the line voltage over the battery counter voltage and give a proper amperage. This is an example of where a fixed residual resistance is desirable in the rheosta't and the resistance elements 35 and 36 constitute such a proper residual resistance. When the arm 12 is at the position 12 in Fig. 1, 'a maximum current will flow and this current can be regulated down to lower amperages by moving the arm 12 to the left and inserting more and more of the resistance 37. Suchrheostats as this are designed so that,'at any stage of adjustment,

the laststep of resistance introduced in the circuit, that is the step nearest the contact arm, is to'be loaded to the maximum watts which it will stand. Of course if the arm 12 moves to the left increasing the resistance, it diminishes the current,-so that the resistance steps 37 must beof increased resistance value to keep the maximum wattage on the last step included inthe circuit.

With only a few steps of adjustable resistance in circuit,each will be loaded to the maximum or nearlyto the maximum, and the current will be high and the residual resistance 35 will be loaded nearly to its maximum. In this case however, the residualrresistance 35 and the adjustable resistance will be widely separated, and the heat developedin each of these parts will be more readily dissipated than if they were close together. If the semi-adjustable resistance 36 is reduced to nothing so that the arm 12 can go to the extreme right as viewed in Fig. 4:, it will be seen that if only a few steps of adjustable resistance are included, this adjustable resistance and the residual resistance 35 will be widely separated thus promoting the dissipation of their heat.

On the other hand, consider the situation when all the adjustable resistance'is in circuit, that is when the arm 12 is at the left so as to include all the resistance elements 37 to 37. In this case the resistance step 37' close to the arm 12 will be carrying its maximum permissible wattage and will be developin its maximum permissible amount of heat. I3ut at this time, since all the resistance is in circuit, the current will be low, and the residual resistance 35 will not be heated up near to its permissiblemaximum so that there will be no objection to having the resistance 37 adjacent thereto. Thus it will be seen that in this example of my in 'vention as diagram'ed in Fig. 4, when the carrying resistance elements are developing much heat, then these elements will be found separated widely in two parts of the rheostat so as to promote the diffusion of the heat; Only when practically all the resistance is in circuit, will the residual resistance on the left be found adjacentto the most heated adjustable resistance elements 38, but at this time the current magnitude is low so that the heating efi'ect in the residual resistance 35 is moderate and no separation of the resistance elements is needful.

In the problem of designing a rheostat so as to promote the dissipation of heat, one of the measures adopted and exhibited in the embodiment of theinvention shown in the drawings is to distribute the resistance on the two plates 5 and 6. It is evident that in this way an excessively large plate may be avoided such as would be required if a single plate were extended sufficiently to carry all the resistance. Ample ventilation is afforded between the two plates. In addition, as heretofore explained, the resistance is distributed on each plate so that when the current is very large thecurrent carrying resistance elements will be found on the edge portions of the plate thus promoting the dissipation of heat.

The contact carrying arm and other mechdisposed becreased by the inwardly projecting flange 55 around each plate.

The shoes 22 and23 are pushed in. opposite directions by the springs 28 and 29 so that there is a balanced reaction on the'arm 12 and no resultant stress thereon, and accordingly there is no resultant stress on the pivotal support 13. In this way the pivot 13 is protected from becoming worn or loosene In certain of the following sclaims I distinguish between resistance elements according as they are electrically remote or near, or spatially remote or near, for example I consider the resistance elements 35 and 37 to be spatially near but electrically remote; while they are located near together in space, they are separated electrically by the intervening'elements 36 and 37 in sequence along the circuit.

I claim 1. In a rheostat, a fixed resistance, a variable resistance' connected in series with said fixed resistance, said fixed resistance being more remotely located from that part of the variable resistance to which it is directly connected than from that part of the variable resistance to which it is connected through a portion of said variable resistance.

2. In a rheostat, a fixed resistance divided into two portions, a variable resistance in circuit therewith, said variable resistance being located between said two portions of fixed resistance.

3. In a rheostat, two parallel plates, resistance elements supported on the inner faces of said plates, two opposed rows of contacts mounted respectively on the inner faces of said plates, a contact arm between said plates, a rotatable mounting for said arm carried by one of said plates, and opposite spring pressed shoes carried by said arm and engaging said rows of contacts respectively.

1. In a rheostat, two parallel metal plates, insulating enamel coatings on the inner faces of said plates, resistance elements embedded in said coatings, exposed contact buttons engaging said elements and projecting toward each other in two opposite rows, an arm between said rows of contact buttons, a rotatable mounting for said arm located between said plates and opposite spring pressed shoes carried by said arm and engaging said rows of contacts respectively.-

5. In a rheostat, two parallel plates, resistance elements on the inner faces thereof and facing each other, two opposed rows of contacts mounted on the inner faces of said plates, a pivoted arm between the plates engaging said rows of contacts simultaneously, the end of said arm projecting from between the plates, and a handle on said end.

6. In a rheostat, two parallel metal plates, enamel coatings on the inner faces thereof and facing eachother, resistance elements embedded in said coatings, and operating mechanism between said plates for adjusting the amount of resistance elements in circuit.

7. In a rheostat, two parallel opposed plates, resistance elements mounted on the inner faces of saidplates, a pivoted contact arm pivotally mounted between said plates adapted for engagement with said elements, the end of said arm projecting from between the plates and a handle projecting from the end of said arm transversely to the plane of one of said plates. 7

8. In a rheostat, a plate, two sets of resistance elements carried thereby, one of which may be cut out in operation while the other may remain in circuit in operation, said last mentioned set being disposed in parts widely separated from each other on different regions of said plate.

9. In a rheostat, a metal plate, a coating of enamel thereon, two sets of resistance elements embedded in said enamel, one of which may be cut out in operation while the other may remain in circuit in operation, said last mentioned set being widely scattered on different parts of the plate.

10. In a rheostat, a plate, and two sets of resistance elements carried thereby, one set being centrally located on the plate and adapted to be cut out in operation, the other set being located on the plate on both sides of said centrally located set and adapted to remain in circuit in operation after the first set has been cut out.

11. In a rheostat, two sets of resistance elements, one of which may be cut out in operation while the other may remain in circuit in operation, the first set being located centrally in the rheostat and the other set being located near two opposite edges of the rheostat.

12. In a rheostat, a metal plate, an enamel coating thereon, resistance elements imbedded in said enamel, part of said elements being residual and disposed in series at the opposite edges of the plate and the remainder of said elements being adjustable and disposed at the intermediate portion of the plate.

13. In a rheostat, two parallel metal plates with enamel coatings on the inner faces thereof, resistance elements embedded in said enamel coatings, adjustable means for making connection with certain of said elements on the respective plates and two terminal members for the rheostat with connections therefrom through the resistance elements on the respective plates alike in multiple.

14. In a rheostat, a plurality of series connected resistance elements, a movable contact member to engage one of them, a permanent circuit connection at one end of the series, and another permanent circuit connection to said movable contact member,

certain electrically intermediate elements of the series being spatially remote from the elements that are electrically nearest to the first mentioned terminal.

15. In a rheostat, residual resistance elements semi-adjustable resistance elements and fully ad ustable res1stance elements all connected in series, said semi-adjustable elemember to engagesaid adjustable steps, the earlier steps to be out out in moving the contact member from the position in Which the resistance is all connected in circuit being spatially nearest to SEIiClIGSlClHfll resistance elements.

17. In a rheostat resistance elements connected in series a movable contact arm ad 7 justably to engage certain of said elements,

and means Widely separating the elements that remain in circuit for that adjustment which gives a reduced number of the elements in circult.

LEONARD KEBLVER. 

